The invention concerns an apparatus for testing the diameter of a cylindrical hole machined in a very thick part, in two different planes through the axis of the hole and along its entire length.
In the manufacture of steam generators, such as steam generators used in pressurized water nuclear reactors, it is necessary to carry out dimension testing of cylindrical holes passing through the tube sheet, after they have been machined.
In practice, these very long cylindrical holes passing through the tube sheet receive the tubes of the bank which are secured inside these holes in the tube sheet by flanging over.
To assure a good join between the tubes and the sheet, it is therefore necessary for all the holes in the tube sheet to be of constant section over the whole thickness of the sheet.
To test that this section of the hole is truly constant, over the whole extent of the sheet, measurements must be made over the whole length of the boring, and in the different axial planes, i.e., passing through the axis of the hole.
The testing of diameters is generally carried out in two perpendicular axial planes and over the whole length of the hole through the tube sheet.
To carry out this dimension testing, a manually controlled apparatus is used, allowing a plug bearing a feeler, such as an electronic feeler, to be moved inside the hole allowing the values of the diameter to be displayed very accurately on a display screen.
Complete scanning of the entire length of the hole in two axial planes forming an angle of 90.degree. is carried out for each hole.
This method of testing is not, however, entirely satisfactory because of the inaccuracy of the measurements, due to the fact that the speed of movement of the plug bearing the measuring feeler is not constant and that the position of the feeler along the length of the hole during measurements is not known accurately.
In addition, movement by manual means of the measuring plug which has to be duplicated for each hole passing through the tube sheet is a lengthy and difficult operation to carry out.
An apparatus described in French Pat. No. 2,386,803 and allows some automation of the operations involved in dimension-testing a bore.
The apparatus described comprises a measuring head with movable contacts angularly movable by a system of pawls when the apparatus is positioned and axially secured in the bore.
The measurement can be displayed either on the body of the apparatus or on a separate recording unit.
Such an apparatus allows dimension faults in the bore to be detected in a radial plane but not in angularly disposed, axial planes.
There is therefore no known apparatus capable of carrying out dimension testing over the whole length of a hole made in a very thick part and in different axial planes.
The object of the invention is therefore an apparatus for testing the diameter of a cylindrical hole machined in a very thick part, in two different planes passing through the axis of the hole and proceeding over its entire length, this apparatus allowing uniform and exact movements of a diameter-measuring apparatus to be carried out and testing to be carried out rapidly and automatically.